The invention relates to an ultrasonic distance-measuring method and device.
A known ultrasonic distance-measuring method is disclosed, for example, in German Patent 19744185 A1, which describes the use of a plurality of ultrasonic transducers in an ultrasonic distance-measuring method for passenger cars. The same transducers are used for both transmission and reception. Long transmitter pulses are used for large ranges and short transmitter pulses for short ranges. The pulse length can be toggled. The short pulse lengths belong to a sequential operation, whereas the long pulse lengths are used during simultaneous operation of a plurality of ultrasonic transducers. Alternatively, long pulses can also be used if no echo has been detected with short pulses.
A disadvantage of the known arrangement is that the pulse lengths are indeed optimized for both short and long distances, but can be unfavorable for intermediate distances. In this situation, the decay behavior (diagnosis echo) of the ultrasonic generator used can have a negative influence since, if it lasts too long, the diagnosis echo can mask reflected pulses of near objects.
From German Patent 19607788 A1, it is further known that ultrasonic distance measurement can be used in a vehicle reversing toward an obstruction. If an obstruction is detected in this way, the vehicle speed in a first range of distance to the obstruction is limited by control of the power of the drive unit of the vehicle, while in a second range of distance, braking force is built up in the wheel brakes of the vehicle.